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Ignition circuit issue.

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  Ignition circuit issue. Sylvia Else <sylvia@not.at.this.address> - 2017-03-26 15:36 +1100
    Re: Ignition circuit issue. John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-25 22:33 -0700
      Re: Ignition circuit issue. Sylvia Else <sylvia@not.at.this.address> - 2017-03-26 17:33 +1100
        Re: Ignition circuit issue. Larry Sheldon <lfsheldon@gmail.com> - 2017-03-27 00:54 -0500
          Re: Ignition circuit issue. Sylvia Else <sylvia@not.at.this.address> - 2017-03-27 19:34 +1100
        Re: Ignition circuit issue. dagmargoodboat@yahoo.com - 2017-03-27 07:16 -0700
          Re: Ignition circuit issue. makolber@yahoo.com - 2017-03-27 09:18 -0700
          Re: Ignition circuit issue. Sylvia Else <sylvia@not.at.this.address> - 2017-03-28 11:13 +1100
    Re: Ignition circuit issue. Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-03-27 16:25 -0700
      Re: Ignition circuit issue. Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-03-27 16:31 -0700
        Re: Ignition circuit issue. Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-03-27 16:36 -0700
        Re: Ignition circuit issue. Sylvia Else <sylvia@not.at.this.address> - 2017-03-28 15:19 +1100
          Re: Ignition circuit issue. Neon John <no@never.com> - 2017-03-31 14:41 -0400
            Re: Ignition circuit issue. Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-03-31 11:55 -0700
      Re: Ignition circuit issue. Sylvia Else <sylvia@not.at.this.address> - 2017-03-28 12:03 +1100
        Re: Ignition circuit issue. piglet <erichpwagner@hotmail.com> - 2017-03-28 08:39 +0100
          Re: Ignition circuit issue. Sylvia Else <sylvia@not.at.this.address> - 2017-03-28 20:54 +1100

#453681 — Ignition circuit issue.

I'm using this circuit to provide 250V pulses to an ignition coil.

https://www.dropbox.com/s/1w33uss3eedem05/ignition2.pdf?dl=0

The IC is a Linear Technology LT1243.

12V is provided on G$1 to the left. G$2 accepts a trigger pulse, and G$3 
is ground.

LTSpice says that this works, and indeed the real implementation does. 
Mostly.

The difference is that after the circuit has been triggered once, it 
won't charge the capacitor again (above about 25 volts) for a varying 
period that can be up to half a minute. It's as if the wrong level is 
being used internally to compare with the feedback pin. In that regard, 
I'll mention that Q3 is used to pull FB up so that the circuit stops 
driving the FET, since otherwise the SCR never turns off. I've checked, 
and the problem is not that Q3 remains on, nor is it that the SCR fails 
to turn off. In any case, the 1.5uF capacitor C1 does get charged 
somewhat, as I mentioned above.

When the issue resolves, it does so rapidly, within a fraction of a second.

Connecting an oscilloscope probe to the RT/CT pin of the IC restores 
function, but only if the scope is set to DC coupling - not AC coupling 
- and functioning continues only as long as the probe remains connected 
- until the aforesaid varying period has elapsed. Touching the pin with 
a finger has a similar effect.

That is, connect probe; works. Disconnect; stops working. Reconnect; 
works, etc. until eventually it starts working continuously.

This cannot be capacitive loading - there's already a significant 
capacitance between RT/CT and ground.

The fact that the coupling has to be DC made me think that some small 
current was flowing to ground through the scope, so I bridged C4 with a 
100K resistor. It didn't make any difference.

I tried changing the IC (a pain, given that it's surface mounted), but 
again it made no difference.

Any other ideas about what might be happening here.

Sylvia.

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#453684

On Sun, 26 Mar 2017 15:36:06 +1100, Sylvia Else
<sylvia@not.at.this.address> wrote:

>I'm using this circuit to provide 250V pulses to an ignition coil.
>
>https://www.dropbox.com/s/1w33uss3eedem05/ignition2.pdf?dl=0
>
>The IC is a Linear Technology LT1243.
>
>12V is provided on G$1 to the left. G$2 accepts a trigger pulse, and G$3 
>is ground.
>
>LTSpice says that this works, and indeed the real implementation does. 
>Mostly.
>
>The difference is that after the circuit has been triggered once, it 
>won't charge the capacitor again (above about 25 volts) for a varying 
>period that can be up to half a minute. It's as if the wrong level is 
>being used internally to compare with the feedback pin. In that regard, 
>I'll mention that Q3 is used to pull FB up so that the circuit stops 
>driving the FET, since otherwise the SCR never turns off. I've checked, 
>and the problem is not that Q3 remains on, nor is it that the SCR fails 
>to turn off. In any case, the 1.5uF capacitor C1 does get charged 
>somewhat, as I mentioned above.
>
>When the issue resolves, it does so rapidly, within a fraction of a second.
>
>Connecting an oscilloscope probe to the RT/CT pin of the IC restores 
>function, but only if the scope is set to DC coupling - not AC coupling 
>- and functioning continues only as long as the probe remains connected 
>- until the aforesaid varying period has elapsed. Touching the pin with 
>a finger has a similar effect.
>
>That is, connect probe; works. Disconnect; stops working. Reconnect; 
>works, etc. until eventually it starts working continuously.
>
>This cannot be capacitive loading - there's already a significant 
>capacitance between RT/CT and ground.
>
>The fact that the coupling has to be DC made me think that some small 
>current was flowing to ground through the scope, so I bridged C4 with a 
>100K resistor. It didn't make any difference.
>
>I tried changing the IC (a pain, given that it's surface mounted), but 
>again it made no difference.
>
>Any other ideas about what might be happening here.
>
>Sylvia.

Just possibly the SCR is staying on, shorts the inverter, which
thermal limits, and recovers later? It's awfully complex.


Back when it wasn't so lethal to ride motorcycles on the street (and I
wasn't too bright) I use to make my own CD ignitions.

I liked this topology

https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/CDI.jpg

because it was easy to drive the SCR gate with a simple RC circuit
from the points. A low value resistor from gate to ground ensures
turnoff. You could elect to kill the boost converter during the gate
pulse, too.

To get a fat spark, you need a pretty wide SCR gate pulse, to let the
whole mess ring a few cycles. I usually ran around 80 to 100 mJ per
spark, which will fire a plug no matter how fouled. Barely needs
gasoline.

Actually, my HV supplies were open-loop 2-transistor DC/DC converters
with full bridge rectifiers. It sort of relaxed for a while after
being shorted, then started oscillating again, which was nice.


-- 

John Larkin         Highland Technology, Inc

lunatic fringe electronics 

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#453696

On 26/03/2017 4:33 PM, John Larkin wrote:
> On Sun, 26 Mar 2017 15:36:06 +1100, Sylvia Else
> <sylvia@not.at.this.address> wrote:
>
>> I'm using this circuit to provide 250V pulses to an ignition coil.
>>
>> https://www.dropbox.com/s/1w33uss3eedem05/ignition2.pdf?dl=0
>>
>> The IC is a Linear Technology LT1243.
>>
>> 12V is provided on G$1 to the left. G$2 accepts a trigger pulse, and G$3
>> is ground.
>>
>> LTSpice says that this works, and indeed the real implementation does.
>> Mostly.
>>
>> The difference is that after the circuit has been triggered once, it
>> won't charge the capacitor again (above about 25 volts) for a varying
>> period that can be up to half a minute. It's as if the wrong level is
>> being used internally to compare with the feedback pin. In that regard,
>> I'll mention that Q3 is used to pull FB up so that the circuit stops
>> driving the FET, since otherwise the SCR never turns off. I've checked,
>> and the problem is not that Q3 remains on, nor is it that the SCR fails
>> to turn off. In any case, the 1.5uF capacitor C1 does get charged
>> somewhat, as I mentioned above.
>>
>> When the issue resolves, it does so rapidly, within a fraction of a second.
>>
>> Connecting an oscilloscope probe to the RT/CT pin of the IC restores
>> function, but only if the scope is set to DC coupling - not AC coupling
>> - and functioning continues only as long as the probe remains connected
>> - until the aforesaid varying period has elapsed. Touching the pin with
>> a finger has a similar effect.
>>
>> That is, connect probe; works. Disconnect; stops working. Reconnect;
>> works, etc. until eventually it starts working continuously.
>>
>> This cannot be capacitive loading - there's already a significant
>> capacitance between RT/CT and ground.
>>
>> The fact that the coupling has to be DC made me think that some small
>> current was flowing to ground through the scope, so I bridged C4 with a
>> 100K resistor. It didn't make any difference.
>>
>> I tried changing the IC (a pain, given that it's surface mounted), but
>> again it made no difference.
>>
>> Any other ideas about what might be happening here.
>>
>> Sylvia.
>
> Just possibly the SCR is staying on, shorts the inverter, which
> thermal limits, and recovers later? It's awfully complex.

I don't see any sign of that - the voltage across the coil is zero at 
this point, whereas the capacitor C1 has about 25V across it, dropping 
to zero each time the circuit is triggered, and then climbing back toe 
25V. The scope shows a few steps, as it gets pumped to there, but it 
doesn't continue upwards.

>
>
> Back when it wasn't so lethal to ride motorcycles on the street (and I
> wasn't too bright) I use to make my own CD ignitions.
>
> I liked this topology
>
> https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/CDI.jpg
>
> because it was easy to drive the SCR gate with a simple RC circuit
> from the points. A low value resistor from gate to ground ensures
> turnoff. You could elect to kill the boost converter during the gate
> pulse, too.
>
> To get a fat spark, you need a pretty wide SCR gate pulse, to let the
> whole mess ring a few cycles. I usually ran around 80 to 100 mJ per
> spark, which will fire a plug no matter how fouled. Barely needs
> gasoline.

Looks like I'm using a bit under 50mJ, which seems to be working, albeit 
with a plug in reasonable condition.

>
> Actually, my HV supplies were open-loop 2-transistor DC/DC converters
> with full bridge rectifiers. It sort of relaxed for a while after
> being shorted, then started oscillating again, which was nice.
>
>

My application is the engine of a generator. It doesn't have points, but 
has some magnet/coil arrangement that produces a pulse at the correct 
point in the cycle.

Certainly charging through the coil simplifies things, but I had/have no 
idea what the inductance of the coil might be. Indeed, it turned out 
that my coil had insulation failure in the HT side, and I had to source 
a new one, so even if I'd tried to measure the old one, the new one 
could have been different.

Finally got the engine running today, using this ignition circuit, and 
LPG, after many hours spent cursing a PIC32MX that I was temporarily 
using to generate the trigger pulse - got caught out by yet another PIC 
errata - input capture doesn't work when the processor is in the idle state.

Sylvia.

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#453845

On 3/26/2017 01:33, Sylvia Else wrote:
> On 26/03/2017 4:33 PM, John Larkin wrote:
>> On Sun, 26 Mar 2017 15:36:06 +1100, Sylvia Else
>> <sylvia@not.at.this.address> wrote:
>>
>>> I'm using this circuit to provide 250V pulses to an ignition coil.
>>>
>>> https://www.dropbox.com/s/1w33uss3eedem05/ignition2.pdf?dl=0
>>>
>>> The IC is a Linear Technology LT1243.
>>>
>>> 12V is provided on G$1 to the left. G$2 accepts a trigger pulse, and G$3
>>> is ground.
>>>
>>> LTSpice says that this works, and indeed the real implementation does.
>>> Mostly.
>>>
>>> The difference is that after the circuit has been triggered once, it
>>> won't charge the capacitor again (above about 25 volts) for a varying
>>> period that can be up to half a minute. It's as if the wrong level is
>>> being used internally to compare with the feedback pin. In that regard,
>>> I'll mention that Q3 is used to pull FB up so that the circuit stops
>>> driving the FET, since otherwise the SCR never turns off. I've checked,
>>> and the problem is not that Q3 remains on, nor is it that the SCR fails
>>> to turn off. In any case, the 1.5uF capacitor C1 does get charged
>>> somewhat, as I mentioned above.
>>>
>>> When the issue resolves, it does so rapidly, within a fraction of a
>>> second.
>>>
>>> Connecting an oscilloscope probe to the RT/CT pin of the IC restores
>>> function, but only if the scope is set to DC coupling - not AC coupling
>>> - and functioning continues only as long as the probe remains connected
>>> - until the aforesaid varying period has elapsed. Touching the pin with
>>> a finger has a similar effect.
>>>
>>> That is, connect probe; works. Disconnect; stops working. Reconnect;
>>> works, etc. until eventually it starts working continuously.
>>>
>>> This cannot be capacitive loading - there's already a significant
>>> capacitance between RT/CT and ground.
>>>
>>> The fact that the coupling has to be DC made me think that some small
>>> current was flowing to ground through the scope, so I bridged C4 with a
>>> 100K resistor. It didn't make any difference.
>>>
>>> I tried changing the IC (a pain, given that it's surface mounted), but
>>> again it made no difference.
>>>
>>> Any other ideas about what might be happening here.
>>>
>>> Sylvia.
>>
>> Just possibly the SCR is staying on, shorts the inverter, which
>> thermal limits, and recovers later? It's awfully complex.
>
> I don't see any sign of that - the voltage across the coil is zero at
> this point, whereas the capacitor C1 has about 25V across it, dropping
> to zero each time the circuit is triggered, and then climbing back toe
> 25V. The scope shows a few steps, as it gets pumped to there, but it
> doesn't continue upwards.
>
>>
>>
>> Back when it wasn't so lethal to ride motorcycles on the street (and I
>> wasn't too bright) I use to make my own CD ignitions.
>>
>> I liked this topology
>>
>> https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/CDI.jpg
>>
>> because it was easy to drive the SCR gate with a simple RC circuit
>> from the points. A low value resistor from gate to ground ensures
>> turnoff. You could elect to kill the boost converter during the gate
>> pulse, too.
>>
>> To get a fat spark, you need a pretty wide SCR gate pulse, to let the
>> whole mess ring a few cycles. I usually ran around 80 to 100 mJ per
>> spark, which will fire a plug no matter how fouled. Barely needs
>> gasoline.
>
> Looks like I'm using a bit under 50mJ, which seems to be working, albeit
> with a plug in reasonable condition.
>
>>
>> Actually, my HV supplies were open-loop 2-transistor DC/DC converters
>> with full bridge rectifiers. It sort of relaxed for a while after
>> being shorted, then started oscillating again, which was nice.
>>
>>
>
> My application is the engine of a generator. It doesn't have points, but
> has some magnet/coil arrangement that produces a pulse at the correct
> point in the cycle.

I just sortakinda fell into this thread and I do not have the 
credentials to be jumping in, but I do have to say that that that 
"magnet/coil arrangement"  is called a "magneto" on the backyard and 
shade-tree mechanic circuits I used to hand on, and it puts out a 
shocking pulse tall enough to fire a plug on a good day.

> Certainly charging through the coil simplifies things, but I had/have no
> idea what the inductance of the coil might be. Indeed, it turned out
> that my coil had insulation failure in the HT side, and I had to source
> a new one, so even if I'd tried to measure the old one, the new one
> could have been different.
>
> Finally got the engine running today, using this ignition circuit, and
> LPG, after many hours spent cursing a PIC32MX that I was temporarily
> using to generate the trigger pulse - got caught out by yet another PIC
> errata - input capture doesn't work when the processor is in the idle
> state.
>
> Sylvia.
>
>
>
>
>
>
>
>


-- 
quis custodiet ipsos custodes?
-- Juvenal

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#453850

On 27/03/2017 4:54 PM, Larry Sheldon wrote:
> On 3/26/2017 01:33, Sylvia Else wrote:

>> My application is the engine of a generator. It doesn't have points, but
>> has some magnet/coil arrangement that produces a pulse at the correct
>> point in the cycle.
>
> I just sortakinda fell into this thread and I do not have the
> credentials to be jumping in, but I do have to say that that that
> "magnet/coil arrangement"  is called a "magneto" on the backyard and
> shade-tree mechanic circuits I used to hand on, and it puts out a
> shocking pulse tall enough to fire a plug on a good day.

There are such things, but this is not that. As originally supplied it 
was an ordinary capacitive discharge ignition. There's a separate 
winding that produces the power used to energise the capacitor, and then 
this magnet and coil device is used to produce a pulse that triggers the 
discharge into the coil.

Sylvia.

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#453869

On Sunday, March 26, 2017 at 2:33:13 AM UTC-4, Sylvia Else wrote:

> Finally got the engine running today, using this ignition circuit, and 
> LPG, after many hours spent cursing a PIC32MX that I was temporarily 
> using to generate the trigger pulse - got caught out by yet another PIC 
> errata - input capture doesn't work when the processor is in the idle state.
> 
> Sylvia.

Was that PIC quirk the problem?  Otherwise, I'd ask
o  Whether C4 might be bad, open, or the wrong value?

Or, that not being the case, maybe the LT1243's upset about having its
FB pin pulled all the way to +5v (wind-up?)?

Is the LT1243's Vref getting glitched from your reset circuit, upsetting
the LT?

Just some wild ideas.  From your description it really sounds like it's
RT/CT pin-related, and you've already put your finger on it (so to speak :).

Cheers,
James Arthur

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#453885

> 
> Is the LT1243's Vref getting glitched from your reset circuit, upsetting
> the LT?
>

or are there invisible glitches on the feedback pin, try removing C5?

m

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#453935

On 28/03/2017 1:16 AM, dagmargoodboat@yahoo.com wrote:
> On Sunday, March 26, 2017 at 2:33:13 AM UTC-4, Sylvia Else wrote:
>
>> Finally got the engine running today, using this ignition circuit, and
>> LPG, after many hours spent cursing a PIC32MX that I was temporarily
>> using to generate the trigger pulse - got caught out by yet another PIC
>> errata - input capture doesn't work when the processor is in the idle state.
>>
>> Sylvia.
>
> Was that PIC quirk the problem?  Otherwise, I'd ask
> o  Whether C4 might be bad, open, or the wrong value?

No, and I even replaced it. Its value is far from critical anyway.
>
> Or, that not being the case, maybe the LT1243's upset about having its
> FB pin pulled all the way to +5v (wind-up?)?

It's within spec. Another possibility is that the LT1243 is interpreting 
the sudden drop in FB as an indicator of an output short, but if so, I'd 
expect it to object to every such occurrence, not just the first.

>
> Is the LT1243's Vref getting glitched from your reset circuit, upsetting
> the LT?
>
> Just some wild ideas.  From your description it really sounds like it's
> RT/CT pin-related, and you've already put your finger on it (so to speak :).

The IC is not really designed with this application in mind. Perhaps it 
just plain doesn't like being used this way.

Sylvia.

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#453930

On Sun, 26 Mar 2017 15:36:06 +1100, Sylvia Else
<sylvia@not.at.this.address> wrote:

>I'm using this circuit to provide 250V pulses to an ignition coil.
>
>https://www.dropbox.com/s/1w33uss3eedem05/ignition2.pdf?dl=0
>
>The IC is a Linear Technology LT1243.
>
>12V is provided on G$1 to the left. G$2 accepts a trigger pulse, and G$3 
>is ground.
>
>LTSpice says that this works, and indeed the real implementation does. 
>Mostly.
>
>The difference is that after the circuit has been triggered once, it 
>won't charge the capacitor again (above about 25 volts) for a varying 
>period that can be up to half a minute. It's as if the wrong level is 
>being used internally to compare with the feedback pin. In that regard, 
>I'll mention that Q3 is used to pull FB up so that the circuit stops 
>driving the FET, since otherwise the SCR never turns off. I've checked, 
>and the problem is not that Q3 remains on, nor is it that the SCR fails 
>to turn off. In any case, the 1.5uF capacitor C1 does get charged 
>somewhat, as I mentioned above.
>
>When the issue resolves, it does so rapidly, within a fraction of a second.
>
>Connecting an oscilloscope probe to the RT/CT pin of the IC restores 
>function, but only if the scope is set to DC coupling - not AC coupling 
>- and functioning continues only as long as the probe remains connected 
>- until the aforesaid varying period has elapsed. Touching the pin with 
>a finger has a similar effect.
>
>That is, connect probe; works. Disconnect; stops working. Reconnect; 
>works, etc. until eventually it starts working continuously.
>
>This cannot be capacitive loading - there's already a significant 
>capacitance between RT/CT and ground.
>
>The fact that the coupling has to be DC made me think that some small 
>current was flowing to ground through the scope, so I bridged C4 with a 
>100K resistor. It didn't make any difference.
>
>I tried changing the IC (a pain, given that it's surface mounted), but 
>again it made no difference.
>
>Any other ideas about what might be happening here.
>
>Sylvia.

Using a PIC when you should have gone analog >:-}

<http://www.analog-innovations.com/SED/CD-Ignition-Basic.pdf>

<http://www.analog-innovations.com/SED/CDI_Inductor.jpg>
		
                                        ...Jim Thompson
-- 
| James E.Thompson                                 |    mens     |
| Analog Innovations                               |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

     Thinking outside the box... producing elegant solutions.

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#453932

Den tirsdag den 28. marts 2017 kl. 01.25.23 UTC+2 skrev Jim Thompson:
> On Sun, 26 Mar 2017 15:36:06 +1100, Sylvia Else
> <sylvia@not.at.this.address> wrote:
> 
> >I'm using this circuit to provide 250V pulses to an ignition coil.
> >
> >https://www.dropbox.com/s/1w33uss3eedem05/ignition2.pdf?dl=0
> >
> >The IC is a Linear Technology LT1243.
> >
> >12V is provided on G$1 to the left. G$2 accepts a trigger pulse, and G$3 
> >is ground.
> >
> >LTSpice says that this works, and indeed the real implementation does. 
> >Mostly.
> >
> >The difference is that after the circuit has been triggered once, it 
> >won't charge the capacitor again (above about 25 volts) for a varying 
> >period that can be up to half a minute. It's as if the wrong level is 
> >being used internally to compare with the feedback pin. In that regard, 
> >I'll mention that Q3 is used to pull FB up so that the circuit stops 
> >driving the FET, since otherwise the SCR never turns off. I've checked, 
> >and the problem is not that Q3 remains on, nor is it that the SCR fails 
> >to turn off. In any case, the 1.5uF capacitor C1 does get charged 
> >somewhat, as I mentioned above.
> >
> >When the issue resolves, it does so rapidly, within a fraction of a second.
> >
> >Connecting an oscilloscope probe to the RT/CT pin of the IC restores 
> >function, but only if the scope is set to DC coupling - not AC coupling 
> >- and functioning continues only as long as the probe remains connected 
> >- until the aforesaid varying period has elapsed. Touching the pin with 
> >a finger has a similar effect.
> >
> >That is, connect probe; works. Disconnect; stops working. Reconnect; 
> >works, etc. until eventually it starts working continuously.
> >
> >This cannot be capacitive loading - there's already a significant 
> >capacitance between RT/CT and ground.
> >
> >The fact that the coupling has to be DC made me think that some small 
> >current was flowing to ground through the scope, so I bridged C4 with a 
> >100K resistor. It didn't make any difference.
> >
> >I tried changing the IC (a pain, given that it's surface mounted), but 
> >again it made no difference.
> >
> >Any other ideas about what might be happening here.
> >
> >Sylvia.
> 
> Using a PIC when you should have gone analog >:-}
> 
> <http://www.analog-innovations.com/SED/CD-Ignition-Basic.pdf>
> 
> <http://www.analog-innovations.com/SED/CDI_Inductor.jpg>

why even bother with CDI? most car do fine with regular coils, many coils even have the driver igbt buildin all you need is a 5V driver for a few ms of 
dwell time  

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#453933

On Mon, 27 Mar 2017 16:31:19 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

>Den tirsdag den 28. marts 2017 kl. 01.25.23 UTC+2 skrev Jim Thompson:
>> On Sun, 26 Mar 2017 15:36:06 +1100, Sylvia Else
>> <sylvia@not.at.this.address> wrote:
>> 
>> >I'm using this circuit to provide 250V pulses to an ignition coil.
>> >
>> >https://www.dropbox.com/s/1w33uss3eedem05/ignition2.pdf?dl=0
>> >
>> >The IC is a Linear Technology LT1243.
>> >
>> >12V is provided on G$1 to the left. G$2 accepts a trigger pulse, and G$3 
>> >is ground.
>> >
>> >LTSpice says that this works, and indeed the real implementation does. 
>> >Mostly.
>> >
>> >The difference is that after the circuit has been triggered once, it 
>> >won't charge the capacitor again (above about 25 volts) for a varying 
>> >period that can be up to half a minute. It's as if the wrong level is 
>> >being used internally to compare with the feedback pin. In that regard, 
>> >I'll mention that Q3 is used to pull FB up so that the circuit stops 
>> >driving the FET, since otherwise the SCR never turns off. I've checked, 
>> >and the problem is not that Q3 remains on, nor is it that the SCR fails 
>> >to turn off. In any case, the 1.5uF capacitor C1 does get charged 
>> >somewhat, as I mentioned above.
>> >
>> >When the issue resolves, it does so rapidly, within a fraction of a second.
>> >
>> >Connecting an oscilloscope probe to the RT/CT pin of the IC restores 
>> >function, but only if the scope is set to DC coupling - not AC coupling 
>> >- and functioning continues only as long as the probe remains connected 
>> >- until the aforesaid varying period has elapsed. Touching the pin with 
>> >a finger has a similar effect.
>> >
>> >That is, connect probe; works. Disconnect; stops working. Reconnect; 
>> >works, etc. until eventually it starts working continuously.
>> >
>> >This cannot be capacitive loading - there's already a significant 
>> >capacitance between RT/CT and ground.
>> >
>> >The fact that the coupling has to be DC made me think that some small 
>> >current was flowing to ground through the scope, so I bridged C4 with a 
>> >100K resistor. It didn't make any difference.
>> >
>> >I tried changing the IC (a pain, given that it's surface mounted), but 
>> >again it made no difference.
>> >
>> >Any other ideas about what might be happening here.
>> >
>> >Sylvia.
>> 
>> Using a PIC when you should have gone analog >:-}
>> 
>> <http://www.analog-innovations.com/SED/CD-Ignition-Basic.pdf>
>> 
>> <http://www.analog-innovations.com/SED/CDI_Inductor.jpg>
>
>why even bother with CDI? most car do fine with regular coils, many coils even have the driver igbt buildin all you need is a 5V driver for a few ms of 
>dwell time  

But can it saw Plexiglas ?>:-}
		
                                        ...Jim Thompson
-- 
| James E.Thompson                                 |    mens     |
| Analog Innovations                               |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

     Thinking outside the box... producing elegant solutions.

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#453952

On 28/03/2017 10:31 AM, Lasse Langwadt Christensen wrote:
> Den tirsdag den 28. marts 2017 kl. 01.25.23 UTC+2 skrev Jim
> Thompson:
>> On Sun, 26 Mar 2017 15:36:06 +1100, Sylvia Else
>> <sylvia@not.at.this.address> wrote:
>>
>>> I'm using this circuit to provide 250V pulses to an ignition
>>> coil.
>>>
>>> https://www.dropbox.com/s/1w33uss3eedem05/ignition2.pdf?dl=0
>>>
>>> The IC is a Linear Technology LT1243.
>>>
>>> 12V is provided on G$1 to the left. G$2 accepts a trigger pulse,
>>> and G$3 is ground.
>>>
>>> LTSpice says that this works, and indeed the real implementation
>>> does. Mostly.
>>>
>>> The difference is that after the circuit has been triggered once,
>>> it won't charge the capacitor again (above about 25 volts) for a
>>> varying period that can be up to half a minute. It's as if the
>>> wrong level is being used internally to compare with the feedback
>>> pin. In that regard, I'll mention that Q3 is used to pull FB up
>>> so that the circuit stops driving the FET, since otherwise the
>>> SCR never turns off. I've checked, and the problem is not that Q3
>>> remains on, nor is it that the SCR fails to turn off. In any
>>> case, the 1.5uF capacitor C1 does get charged somewhat, as I
>>> mentioned above.
>>>
>>> When the issue resolves, it does so rapidly, within a fraction of
>>> a second.
>>>
>>> Connecting an oscilloscope probe to the RT/CT pin of the IC
>>> restores function, but only if the scope is set to DC coupling -
>>> not AC coupling - and functioning continues only as long as the
>>> probe remains connected - until the aforesaid varying period has
>>> elapsed. Touching the pin with a finger has a similar effect.
>>>
>>> That is, connect probe; works. Disconnect; stops working.
>>> Reconnect; works, etc. until eventually it starts working
>>> continuously.
>>>
>>> This cannot be capacitive loading - there's already a
>>> significant capacitance between RT/CT and ground.
>>>
>>> The fact that the coupling has to be DC made me think that some
>>> small current was flowing to ground through the scope, so I
>>> bridged C4 with a 100K resistor. It didn't make any difference.
>>>
>>> I tried changing the IC (a pain, given that it's surface
>>> mounted), but again it made no difference.
>>>
>>> Any other ideas about what might be happening here.
>>>
>>> Sylvia.
>>
>> Using a PIC when you should have gone analog >:-}
>>
>> <http://www.analog-innovations.com/SED/CD-Ignition-Basic.pdf>
>>
>> <http://www.analog-innovations.com/SED/CDI_Inductor.jpg>
>
> why even bother with CDI? most car do fine with regular coils, many
> coils even have the driver igbt buildin all you need is a 5V driver
> for a few ms of dwell time
>

My application is a backup "portable" generator. One useful feature of 
CDI in this application is that it doesn't require a large input 
current, meaning that I can start the generator using cheap dry cells, 
and then let it power itself. No need for limited life failure prone 
rechargeable batteries that need to be kept topped up lest they die.

Sylvia.

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#454444

On Tue, 28 Mar 2017 15:19:59 +1100, Sylvia Else
<sylvia@not.at.this.address> wrote:


>My application is a backup "portable" generator. One useful feature of 
>CDI in this application is that it doesn't require a large input 
>current, meaning that I can start the generator using cheap dry cells, 
>and then let it power itself. No need for limited life failure prone 
>rechargeable batteries that need to be kept topped up lest they die.

And the problem with CDI, which several motorcycle manufacturers and
Mercury Marine discovered the hard way, is that the brief spark is
lousy at igniting less than optimum mixtures.  Sure, it'll fire a plug
dipped in oil but it won't fire a non-optimum mixture.  Something
common when trying to crank an engine under adverse conditions.

The MSD (Multiple Spark Discharge) company solved this problem by
firing up to 8 sparks per ignition event.  That company has been
around for 30 or 40 years now.

I suggest that you scrap that circuit and go back to the pulse
triggered Kettering-type ignition.  A GM HEI module from the 70s up
through when they gained a 5th terminal makes an EXCELLENT controller.
IT will work with points, variable reluctance or pulse input. Adding
external inductance in parallel with the coil will lengthen the spark
and make it more likely to ignite a crappy mixture.

A brand name AGM battery (Enersys Odessey for example) will maintain
most of its charge for a year or more and a Battery Tender costs
almost nothing.

John
John DeArmond
http://www.neon-john.com
http://www.tnduction.com 
Tellico Plains, Occupied TN
See website for email address

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#454448

On Fri, 31 Mar 2017 14:41:00 -0400, Neon John <no@never.com> wrote:

>On Tue, 28 Mar 2017 15:19:59 +1100, Sylvia Else
><sylvia@not.at.this.address> wrote:
>
>
>>My application is a backup "portable" generator. One useful feature of 
>>CDI in this application is that it doesn't require a large input 
>>current, meaning that I can start the generator using cheap dry cells, 
>>and then let it power itself. No need for limited life failure prone 
>>rechargeable batteries that need to be kept topped up lest they die.
>
>And the problem with CDI, which several motorcycle manufacturers and
>Mercury Marine discovered the hard way, is that the brief spark is
>lousy at igniting less than optimum mixtures.  Sure, it'll fire a plug
>dipped in oil but it won't fire a non-optimum mixture.  Something
>common when trying to crank an engine under adverse conditions.
>
>The MSD (Multiple Spark Discharge) company solved this problem by
>firing up to 8 sparks per ignition event.  That company has been
>around for 30 or 40 years now.

Yep.  I devised schemes to do just that when I was at Philco-Ford in
1968 and Dickson Electronics 1970-72... works quite well with this
"self-inverting" method....

<http://www.analog-innovations.com/SED/CD-Ignition-Basic.pdf>

>
>I suggest that you scrap that circuit and go back to the pulse
>triggered Kettering-type ignition.  A GM HEI module from the 70s up
>through when they gained a 5th terminal makes an EXCELLENT controller.
>IT will work with points, variable reluctance or pulse input. Adding
>external inductance in parallel with the coil will lengthen the spark
>and make it more likely to ignite a crappy mixture.
>
>A brand name AGM battery (Enersys Odessey for example) will maintain
>most of its charge for a year or more and a Battery Tender costs
>almost nothing.
>
>John
>John DeArmond
>http://www.neon-john.com
>http://www.tnduction.com 
>Tellico Plains, Occupied TN
>See website for email address
		
                                        ...Jim Thompson
-- 
| James E.Thompson                                 |    mens     |
| Analog Innovations                               |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

     Thinking outside the box... producing elegant solutions.

[toc] | [prev] | [next] | [standalone]

#453936

On 28/03/2017 10:25 AM, Jim Thompson wrote:
> On Sun, 26 Mar 2017 15:36:06 +1100, Sylvia Else
> <sylvia@not.at.this.address> wrote:
>
>> I'm using this circuit to provide 250V pulses to an ignition coil.
>>
>> https://www.dropbox.com/s/1w33uss3eedem05/ignition2.pdf?dl=0
>>
>> The IC is a Linear Technology LT1243.
>>
>> 12V is provided on G$1 to the left. G$2 accepts a trigger pulse,
>> and G$3 is ground.
>>
>> LTSpice says that this works, and indeed the real implementation
>> does. Mostly.
>>
>> The difference is that after the circuit has been triggered once,
>> it won't charge the capacitor again (above about 25 volts) for a
>> varying period that can be up to half a minute. It's as if the
>> wrong level is being used internally to compare with the feedback
>> pin. In that regard, I'll mention that Q3 is used to pull FB up so
>> that the circuit stops driving the FET, since otherwise the SCR
>> never turns off. I've checked, and the problem is not that Q3
>> remains on, nor is it that the SCR fails to turn off. In any case,
>> the 1.5uF capacitor C1 does get charged somewhat, as I mentioned
>> above.
>>
>> When the issue resolves, it does so rapidly, within a fraction of a
>> second.
>>
>> Connecting an oscilloscope probe to the RT/CT pin of the IC
>> restores function, but only if the scope is set to DC coupling -
>> not AC coupling - and functioning continues only as long as the
>> probe remains connected - until the aforesaid varying period has
>> elapsed. Touching the pin with a finger has a similar effect.
>>
>> That is, connect probe; works. Disconnect; stops working.
>> Reconnect; works, etc. until eventually it starts working
>> continuously.
>>
>> This cannot be capacitive loading - there's already a significant
>> capacitance between RT/CT and ground.
>>
>> The fact that the coupling has to be DC made me think that some
>> small current was flowing to ground through the scope, so I bridged
>> C4 with a 100K resistor. It didn't make any difference.
>>
>> I tried changing the IC (a pain, given that it's surface mounted),
>> but again it made no difference.
>>
>> Any other ideas about what might be happening here.
>>
>> Sylvia.
>
> Using a PIC when you should have gone analog >:-}

Nah! Used a boost converter chip when I should have used a PIC. A 28 pin 
PIC32MX seems a bit over the top for this, but what the hell? It's not 
even more expensive.

>
> <http://www.analog-innovations.com/SED/CD-Ignition-Basic.pdf>
>
> <http://www.analog-innovations.com/SED/CDI_Inductor.jpg>  ...Jim
> Thompson
>

Don't quite see how that works - does it rely on the reverse breakdown
of D3?

Sylvia.

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#453964

On 28/03/2017 02:03, Sylvia Else wrote:
> On 28/03/2017 10:25 AM, Jim Thompson wrote:
>>
>> <http://www.analog-innovations.com/SED/CD-Ignition-Basic.pdf>
>>
>> <http://www.analog-innovations.com/SED/CDI_Inductor.jpg>  ...Jim
>> Thompson
>>
>
> Don't quite see how that works - does it rely on the reverse breakdown
> of D3?
>
> Sylvia.
>

D3 acts normally, the output is a large negative spike.

piglet

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#453975

On 28/03/2017 6:39 PM, piglet wrote:
> On 28/03/2017 02:03, Sylvia Else wrote:
>> On 28/03/2017 10:25 AM, Jim Thompson wrote:
>>>
>>> <http://www.analog-innovations.com/SED/CD-Ignition-Basic.pdf>
>>>
>>> <http://www.analog-innovations.com/SED/CDI_Inductor.jpg>  ...Jim
>>> Thompson
>>>
>>
>> Don't quite see how that works - does it rely on the reverse breakdown
>> of D3?
>>
>> Sylvia.
>>
>
> D3 acts normally, the output is a large negative spike.
>
> piglet

Yes, I see it now.

Sylvia.

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